As a conventional piezoelectric resonator, for example, the capacitor-built-in type piezoelectric resonator shown in FIG. 8 is known (for example, refer to Patent document 1 listed below). The capacitor-built-in type piezoelectric resonator shown in FIG. 8 is structured so that vibrating electrodes 102 are provided on both principal surfaces of a piezoelectric substrate 101, and a pair of sealing substrates 103 are joined to the piezoelectric substrate 101 via a pair of frames 104 made of a resin material so as to surround the respective vibrating electrodes 102.
The piezoelectric substrate 101 is made of a piezoelectric ceramic material, and constitutes a piezoelectric resonant element by being provided with vibrating electrodes 102 on both principal surfaces. The sealing substrate 103 is made of a ceramic material, and forms a capacitance by means of electrodes provided on upper and lower surfaces thereof. In detail, a capacitance is generated via the sealing substrate 103 between an outer terminal electrode 109 and an inner electrode 106 provided on outside surfaces of the sealing substrate 103, between the outer terminal electrode 109 and a portion of an outer terminal electrode 107 extending to the principal surface of the sealing substrate 103, and between the outer terminal electrode 109 and a portion of an outer terminal electrode 108 extending to the principal surface of the sealing substrate 103.
Such a capacitor-built-in type piezoelectric resonator is produced by coating a frame 104 made of uncured resin onto the upper and lower surfaces of the piezoelectric substrate 101 so as to surround vibrating regions of the vibrating electrodes 102, and thereafter, placing the sealing substrates 103 on the frames 104 and then curing the frames 104. This capacitor-built-in type piezoelectric resonator is thinned by setting the heights of the vibration spaces 105 equal to the thickness of the frames 104.
Patent document 1: Japanese Unexamined Patent Publication No. 03-247010 (1991)